Specialised Cells in Human Biology

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“The cells in your body are tiny-a row of about forty would fit into 1mm. But although they are too small to see with the naked eye their complexity is remarkable. A single cell can be thought of as an organised chemical system, separated from its disorganised surroundings by a membrane” (Boyle et al 1999) First here is a brief summary of major eukaryotic organelles and their structures. The nucleus is the largest and most prominent organelle in the cell. It is usually spherical and about 10um in diameter. It contains the DNA and chromosomes and carries information that allows the cell to divide and carry out its cellular processes. Almost all eukaryote cells have a nucleus. The nucleolus is located in the nucleus it is 1-2 um. Its function is to manufacture ribosomes. The ribosomes are found either free in the cytoplasm or attached to the rough endoplasmic reticulum R.E.R, They are 20nm in size and their function is to synthesise the protein in the cell. The cell surface membrane controls the entry and exit of substances in and out of the cell. It is partially permeable. It separates’ the cells contents from the external environment. It is a double layer of phospholipid molecules around 7-10nm thick. Cytoplasm is a jelly like substance that fills the cell it is around 80% water. This is where cell activities occur and most chemical reactions take place. Organelles are suspended in it. The R.E.R. occurs throughout the cytoplasm, it has an extensive membrane network. Its function is to isolate and transport newly synthesised proteins. The mitochondrion is numerous in cytoplasm and there are usually up to 1000per cell. Its function is aerobic respiration and synthesises most of the A.T.P. for the cell. The smooth endoplasmic reticulum S.E.R. is found in small patches in the cytoplasm, they vary in size and their function is to synthesise lipids and steroids.

The muscle cells (see figure 1) that are found in the muscles that move the bones at joints in the...
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